To build on what you said: Elon Musk also said during one of the Tim Dodd interviews that the shuttle had so many limitations because they locked in the design

To build on what you said: Elon Musk also said during one of the Tim Dodd interviews that the shuttle had so many limitations because they locked in the design too early. One limitation is the difficult, fragile and hard to reuse heat-shield on the shuttle. The NASA approach makes it far to expensive to change the design down the road, since that requires resetting all the analysis. Whereas the SpaceX approach never stopped changing things and always tested them in flight. Much cheaper to take a known good and polished design like Falcon 9 and Crew Dragon and do the analysis after you've proven it works well for non-human flights.